The present invention relates to a driver circuit, an electro-optical device, and an electronic instrument.
As a liquid crystal display (LCD) panel (display panel in a broad sense; electro-optical device in a broader sense) used for electronic instruments such as portable telephones, a simple matrix type LCD panel and an active matrix type LCD panel using a switching element such as a thin film transistor (hereinafter abbreviated as “TFT”) have been known.
The simple matrix method can easily reduce power consumption as compared with the active matrix method. On the other hand, it is difficult to increase the number of colors or display a video image using the simple matrix method. The active matrix method is suitable for increasing the number of colors or displaying a video image, but has difficulty in reducing power consumption.
The simple matrix type LCD panel and the active matrix type LCD panel are driven so that the polarity of the voltage applied to a liquid crystal (electro-optical material in a broad sense) forming a pixel is alternately reversed. As such an alternating drive method, a line inversion drive method and a field inversion drive (frame inversion drive) method are known. In the line inversion drive method, the polarity of the voltage applied to the liquid crystal is reversed in units of one or more scan lines. In the field inversion drive method, the polarity of the voltage applied to the liquid crystal is reversed in field (frame) units.
In this case, the voltage level applied to a pixel electrode forming a pixel can be reduced by changing a common electrode voltage (common voltage) supplied to a common electrode opposite to the pixel electrode at the inversion drive timing.
However, power consumption is increased accompanying charging/discharging the liquid crystal even when using such an alternating drive method. In order to solve this problem, JP-A-2002-244622 discloses technology of reducing power consumption by initializing charges stored in the liquid crystal to zero by short-circuiting two electrodes provided on either side of the liquid crystal during inversion drive, thereby causing the drive voltage to transition to the intermediate voltage before short-circuiting the electrodes, for example.
However, the technology disclosed in JP-A-2002-244622 has a problem in which the effect of reducing power consumption varies depending on the voltage applied to the source line. Therefore, the effect of reducing the amount of charges by charging/discharging the common electrode of which the polarity of the voltage is reversed is insufficient. According to the above technology, the amount of charging/discharging may be increased by short-circuiting the electrodes provided on either side of the liquid crystal depending on the relationship between the voltage applied to the source line and the polarity of the common electrode voltage, whereby the effect of reducing power consumption may be reduced.